JP2009098275A - Light source device and image display device, and light quantity correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device having increased light quantity correction accuracy by correcting a light quantity according to a change in light source characteristic in real time. <P>SOLUTION: The light source device includes: a light source; and a driving signal generating means of supplying a driving signal to the light source, and also includes: a light quantity measuring means of measuring the light quantity of the light source; and a light quantity correcting means which calculates as a light quantity error a difference between a target light quantity corresponding to a gray-scale value indicated by gray-scale data input from the outside and a light quantity measured by the light quantity measuring means, corrects differential efficiency which is defined as an amount of variation in light quantity with respect to the amount of variation in the driving signal of the light source by an integral value of a product of the light quantity error and gray-scale value and also corrects a threshold value of the driving signal minimum-required to make the light source emit the light by an integral value of the light quantity error, and outputs to the driving signal generating means a command signal for generating the driving signal having the differential efficiency and the threshold which have been corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light source device, an image display device, and a light amount correction method.

 2. Description of the Related Art In recent years, a laser scan display that displays an image by raster scanning beam-shaped light such as laser light on a projection surface has attracted attention as one form of an image display device. Since such a laser scan display can express completely black by stopping the supply of laser light, for example, the contrast is very high compared to, for example, a projector using a liquid crystal light valve, and a single laser light is used. Because of its wavelength, its color purity is high, and its high coherence makes it easy to shape the beam (easy to squeeze), so it is expected as a high-quality display that realizes high contrast, high color reproducibility, and high resolution. Has been.

As a laser light source of a laser scan display, a semiconductor laser element such as a laser diode is mainly used. However, the laser characteristics of such a semiconductor laser element change due to a change in temperature, aging, etc. Therefore, it is necessary to correct the laser light quantity so that the image brightness can be obtained.

For example, in Patent Document 1 below, the bias current value of the semiconductor laser element is changed by two or more points, the light emission power of the semiconductor laser element is detected by the received light power detection means, the threshold current value of the semiconductor laser element and the quantum efficiency By detecting the change, etc., the DC bias current of the semiconductor laser element is set in the bias current control means, and the pulse current corresponding to the change in the quantum efficiency etc. is set in the pulse current control means, so that the laser output level Has been disclosed. Further, in Patent Document 2 below, a relational expression between the detected light amount of the laser light source and the set value of the optical output is automatically calculated, and data of this relational expression is set in the optical recording medium drive device. A technique for adjusting the output level is disclosed.
JP-A-7-147446 JP 2003-91853 A

  In this way, when correcting the amount of laser light in response to changes in laser characteristics due to temperature changes or aging deterioration, in order to increase the correction accuracy, the laser characteristics change in real time while actually operating the device. It is desirable to perform light amount correction according to the above, but no means has been presented in the above prior art.

    The present invention has been made in view of the above-described circumstances, and a light source device capable of improving light amount correction accuracy by performing light amount correction according to changes in light source characteristics in real time, and an image including the light source device. It is an object to provide a display device and a light amount correction method.

In order to achieve the above object, a light source device according to the present invention is a light source device including a light source and a drive signal generating unit that supplies a drive signal to the light source, and a light amount measuring unit that measures the light amount of the light source. And the difference between the target light amount corresponding to the gradation value indicated by the gradation data input from the outside and the light amount measured by the light amount measuring means is calculated as a light amount error, and the amount of change in the drive signal of the light source is calculated. The differential efficiency defined by the amount of change in the amount of light is corrected by an integrated value of the product of the light amount error and the gradation value, and the threshold of the drive signal that is the minimum necessary for causing the light source to emit light is A light amount correcting unit that corrects the integrated value of the light amount error and outputs a command signal that generates a drive signal having the corrected differential efficiency and a threshold value to the drive signal generating unit.
According to the light source device having such a feature, a light amount error that is a difference between a target light amount corresponding to a gradation value indicated by gradation data input from the outside and a measured light amount is calculated while driving the light source. The differential efficiency, which is one of the light source characteristic parameters, is corrected by an integrated value of the product of the light amount error and the gradation value, and the threshold value of the drive signal, which is also one of the light source characteristic parameters, is set as the light amount error. A command signal that generates a drive signal having a corrected differential efficiency and a threshold value after correction is output to the drive signal generation means, so that a change in light source characteristics due to a temperature change during operation or the like is output. In addition to performing light amount correction according to the real time, high light amount correction accuracy can be obtained.

Further, in the light source device described above, the drive signal generation unit may perform the gradation based on a gradation value indicated by gradation data input from the outside and a gradation current command signal input from the light amount correction unit. A gradation current generating means for generating a gradation current according to a value; a threshold current generating means for generating a threshold current according to a threshold current command signal input from the light amount correcting means; the gradation current and the threshold Current addition means for supplying the light source with a current added to the light source as the drive signal, and the light amount correction means uses the current value of the first variable corresponding to the differential efficiency as the differential efficiency after correction. The gradation current corresponding to the current value of the first variable is obtained by subtracting a numerical value proportional to the integrated value of the product of the light amount error and the gradation value from the previous value of the first variable. The command signal is sent to the gradation current generating means. And calculating the current value of the second variable corresponding to the threshold as the corrected threshold by subtracting a value proportional to the integrated value of the light amount error from the previous value of the second variable, Preferably, the threshold current command signal corresponding to the current value of the second variable is output to the threshold current generating means.
By adopting such a configuration, while driving the light source, the light amount error that is the difference between the target light amount corresponding to the gradation value indicated by the gradation data input from the outside and the measured light amount is minimized. Such a first variable and a second variable are sequentially obtained, and a gradation current command signal capable of correcting the differential efficiency obtained based on the first variable and the second variable; By outputting a threshold current command signal capable of correcting the threshold current to the drive signal generating means, it is possible to perform light amount correction according to a change in light source characteristics due to a temperature change during operation in real time, High light quantity correction accuracy can be obtained.

Further, in the light source device described above, the light amount correction unit may set an average value of the gradation values or a preset value as a gradation value used when calculating a product of the light amount error and the gradation value. It is preferable to use a gradation value or an intermediate value from the minimum gradation value to the maximum gradation value and a difference between the gradation value.
As a result, even if there is a deviation between the target light amount and the measured light amount, such that the integrated value of the light amount error and the integrated value of the product of the light amount error and the gradation value become substantially zero, It is possible to prevent the integrated value of the product of the light amount error and the gradation value from becoming zero, and it is possible to prevent the correction operation in the light amount correction unit from being stopped.

Further, in the light source device described above, the light amount correction unit is sequentially forgotten from the product value of the past light amount error and the gradation value when obtaining the integrated value of the product of the light amount error and the gradation value. It is preferable to multiply the weighting constants such as the ones that are sequentially forgotten from the past light quantity error values.
When calculating the integrated value of the light intensity error and the integrated value of the product of the light intensity error and the gradation value, it is desirable to emphasize the latest data (the product of the light intensity error and the gradation value). As described above, by multiplying weighting constants that are sequentially forgotten from past data, it is possible to perform light amount correction based on the latest data, and to improve light amount correction accuracy.

Further, in the light source device described above, the light amount correction unit is configured to perform the initial setting operation for correcting the offset of the measurement light amount of the light amount measurement unit when the power is turned on. After obtaining the measurement light quantity as a black level light quantity when the gray scale current command signal, the threshold current command signal and the gray scale data are output to the drive signal generating means, the threshold current command signal is increased and the measurement light quantity is increased. When the value obtained by subtracting the black level light amount from the first set light amount that defines a predetermined brightness is reached, the threshold current command signal is decreased, and the value obtained by subtracting the black level light amount from the measured light amount is black. The threshold current command signal when the second set light amount regarded as a level is reached is set as the initial value of the threshold current command signal, while the gradation indicating the maximum gradation value And the gradation current command signal is increased, and the value obtained by subtracting the black level light amount from the measured light amount reaches the third set light amount that defines the maximum target light emission amount. In this case, it is preferable to set the grayscale current command signal as the initial value of the grayscale current command signal.
Thereby, it is possible to obtain the initial values of the gradation current command signal and the threshold current command signal in which the offset of the measurement light amount possessed by the light amount measurement means is corrected, and it is possible to improve the light amount correction accuracy.

Further, in the light source device described above, the light amount correction means uses the initial value of the threshold current command signal obtained by the initial setting operation as the second variable when obtaining the current value of the second variable for the first time. It is preferable that the initial value of the gradation current command signal is used as the previous value of the first variable when obtaining the current value of the first variable for the first time.
Thereby, the current value of the first second variable and the current value of the first variable can be obtained with high accuracy.

On the other hand, an image display apparatus according to the present invention is an image display apparatus that displays an image by scanning light on a projection surface, and the light source device described above and light generated from a light source in the light source device are transmitted to the image display apparatus. The gradation data representing an image to be displayed is generated based on a scanning unit that scans on the projection surface and a video signal supplied from the outside, and according to the irradiation position of the light on the projection surface. Video signal processing means for outputting gradation data to drive signal generation means and light amount correction means in the light source device.
According to the image display device having such a feature, it is possible to perform light amount correction according to a change in light source characteristics due to a temperature change or the like during a display operation in real time, and to obtain high light amount correction accuracy. The display quality can be improved.

In the image display device described above, the video signal processing unit outputs predetermined gradation data to the drive signal generation unit and the light amount correction unit in the light source device during a period in which light is not scanned on the projection surface. The light amount correction unit performs the correction based on the light amount of the light source according to the predetermined gradation data measured by the light amount measurement unit and the gradation value indicated by the predetermined gradation data. Is preferred.
There is a possibility that the gradation value is biased during the display operation. For example, if there is a very dark image, the light amount cannot be corrected normally. As a countermeasure against this, as described above, in a period in which light is not scanned on the projection surface, that is, a period in which image display is not performed, predetermined gradation data is generated by the video signal processing means and the drive signal generating means in the light source device and The light quantity can be corrected without any problem by outputting the light quantity to the light quantity correction means to cause the light source to emit light and performing the light quantity correction operation by the light quantity correction means.

Furthermore, the light amount correction method according to the present invention is a light amount correction method used in a light source device including a light source and a drive signal generation unit that supplies a drive signal to the light source, and is a first method for measuring the light amount of the light source. The second step of calculating the difference between the target light amount corresponding to the gradation value indicated by the gradation data input from the outside and the light amount measured in the first step as a light amount error, A third step of obtaining an integrated value of a product of a light amount error and the gradation value, and a differential efficiency defined by a change amount of the light amount with respect to a change amount of the drive signal of the light source is expressed as the light amount error and the gradation value. A fourth step of correcting by the integrated value of the product, a fifth step of obtaining the integrated value of the light amount error, and a threshold value of the drive signal that is minimum required for causing the light source to emit light. The sixth step of correcting by the integrated value of A seventh step of outputting a command signal so as to generate a driving signal having a differential efficiency and the threshold after correction to the driving signal generating means, characterized by having a.
According to the light amount correction method having such a feature, it is possible to perform light amount correction according to a change in light source characteristics due to a temperature change during operation in real time, and to obtain high light amount correction accuracy.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration block diagram of an image display device LSD according to the present embodiment. The image display device LSD will be described by exemplifying a laser scan display that scans a laser beam on a screen (projected surface) 100 to display an image.

 As shown in FIG. 1, the image display device LSD according to the present embodiment includes a video signal processing circuit 10, a red laser driver 20R, a green laser driver 20G, a blue laser driver 20B, a red laser diode 30R, a green laser diode 30G, and a blue color. Laser diode 30B, optical axis alignment optical system 40, laser scanning unit 50, scanning drive unit 60, irradiation position detection unit 70, pixel synchronization clock generation circuit 80, photoelectric conversion element 90, I / V converter 91, A / D A converter 92, a light amount correction circuit 93, and D / A converters 94 and 95 are provided.

Among the above components, red laser driver 20R, green laser driver 20G, blue laser driver 20B, red laser diode 30R, green laser diode 30G, blue laser diode 30B, photoelectric conversion element 90, I / V converter 91, A The / D converter 92, the light amount correction circuit 93, and the D / A converters 94 and 95 constitute the light source device in the present invention. Furthermore, the photoelectric conversion element 90, the I / V converter 91, and the A / D converter 92 constitute the light quantity measuring means in the present invention.
The correction system circuit block including the photoelectric conversion element 90, the I / V converter 91, the A / D converter 92, the light amount correction circuit 93, and the D / A converters 94 and 95 includes a red laser driver 20R and a green laser driver. 20G and blue laser driver 20B are provided corresponding to each driver (that is, corresponding to each color). However, in FIG. 1, only the correction system circuit block corresponding to red laser driver 20R is shown for convenience of explanation. This is representatively shown.

 A video signal processing circuit (video signal processing means) 10 receives a video signal and a synchronization signal (vertical synchronization signal Vsync and horizontal synchronization signal Hsync) transmitted from an external image supply device (not shown) such as a notebook computer. Based on the video signal and the synchronization signal as input, digital gradation data defining gradation values corresponding to each pixel of the image to be displayed is generated, and the digital gradation data is stored in the internal memory in units of one frame. To do. In the present embodiment, for convenience of explanation, the bit number N of the digital gradation data is set to 4. That is, the image display apparatus LSD can display an image with 16 gradations (4096 colors) from “0” to “15”.

 The video signal processing circuit 10 also has a pulse-shaped frame timing signal Ft that defines the start of one frame and a pulse-shaped signal that defines the start and end of one horizontal scanning period, which are input from the irradiation position detector 70. Based on the scanning timing signal St, the digital gradation data stored in the internal memory is read, and the laser light corresponding to each pixel in one horizontal scanning period input from the pixel synchronous clock generation circuit 80 is read. In synchronization with the pulsed pixel synchronization clock signal CL that defines the irradiation timing, the digital gradation data of the pixel corresponding to the irradiation position of the laser beam is output to the red laser driver 20R, the green laser driver 20G, and the blue laser driver 20B. . More specifically, when the pixel corresponding to the irradiation position of the laser beam is a red pixel, the video signal processing circuit 10 outputs the red gradation data DR for the red pixel to the red laser driver 20R, and the laser beam When the pixel corresponding to the irradiation position is a green pixel, the green gradation data DG for the green pixel is output to the green laser driver 20G, and the pixel corresponding to the laser light irradiation position is a blue pixel The blue gradation data DB for the blue pixel is output to the blue laser driver 20B. The video signal processing circuit 10 outputs the red gradation data DR to the light amount correction circuit 93 of the red correction system circuit block, and outputs the green gradation data DG to the light amount correction circuit of the green correction system circuit block. (Not shown) and the blue gradation data DB is outputted to the light amount correction circuit (not shown) of the blue correction system circuit block.

 The red laser driver (drive signal generating means) 20R includes the red gradation data DR, the threshold current command voltage Vapc1 output from the light amount correction circuit 93 via the D / A converter 94, and the light amount correction circuit 93 to D. The grayscale current command voltage Vapc2 output via the A / A converter 95 is input, and the laser drive current IR corresponding to the red grayscale data DR using the threshold current command voltage Vapc1 and the grayscale current command voltage Vapc2 is input. Is output to the red laser diode 30R. Hereinafter, a detailed configuration of the red laser driver 20R will be described.

 FIG. 2 is a configuration block diagram of the red laser driver 20R. As shown in FIG. 2, the red laser driver 20 </ b> R includes a gradation current generation unit 200, a threshold current generation unit 201, and a current addition unit 202.

 The gradation current generation unit (gradation current generation means) 200 has a gradation current Id (= H1 ·) that is a product of the gradation value D indicated by the red gradation data DR, the gradation current command voltage Vapc2, and the coefficient H1. Vapc2 · D) is generated, and the gradation current Id is output to the current adder 202. The threshold current generation unit (threshold current generation means) 201 generates a threshold current Ith (= H2 · Vapc1) that is the product of the threshold current command voltage Vapc1 and the coefficient H2, and outputs the threshold current Ith to the current addition unit 202. To do. The current adding unit (current adding means) 202 adds the gradation current Id and the threshold current Ith, and outputs the added current to the red laser diode 30R as the laser drive current IR (= Id + Ith).

 FIG. 3 shows a specific circuit configuration diagram of the red laser driver 20R configured as described above. As shown in FIG. 3, the red laser driver 20R includes a first current source CS1, a second current source CS2, a first input side transistor Ti1, a second input side transistor Ti2, and a first output side transistor. To1, second output side transistor To2, third output side transistor To3, fourth output side transistor To4, fifth output side transistor To5, first switch element SW1, second switch element SW2, third Switch element SW3 and fourth switch element SW4.

 The first current source CS1 receives the gradation current command voltage Vapc2 and generates a current Is (= H1 · Vapc2) that is a product of the gradation current command voltage Vapc2 and the coefficient H1. The input terminal is connected to the power supply line Vcc, and the output terminal is connected to the drain terminal and the gate terminal of the first input side transistor Ti1.

 The first input side transistor Ti1 is an n-channel MOS (Positive Metal Oxide Semiconductor) transistor, the drain terminal is connected to the output terminal of the first current source CS1, and the gate terminal is the first current source CS1. The output terminal is connected to the gate terminals of the first output side transistor To1 to the fourth output side transistor To4, and the source terminal is connected to the ground line.

 The first output side transistor To1 is an n-channel type MOS transistor, the drain terminal is connected to one terminal of the first switch element SW1, and the gate terminal is the first input side transistor Ti1 and the second output. The side transistors To2 to To4 are connected to the gate terminals, and the source terminals are connected to the ground line.

 The second output side transistor To2 is an n-channel MOS transistor, the drain terminal is connected to one terminal of the second switch element SW2, the gate terminal is the first input side transistor Ti1, and the first output. The side transistor To1, the third output side transistor To3, and the fourth output side transistor To4 are connected to the gate terminals, and the source terminal is connected to the ground line.

 The third output-side transistor To3 is an n-channel MOS transistor, the drain terminal is connected to one terminal of the third switch element SW3, the gate terminal is the first input-side transistor Ti1, and the first output The side terminal To1, the second output side transistor To2, and the fourth output side transistor To4 are connected to the gate terminals, and the source terminal is connected to the ground line.

 The fourth output-side transistor To4 is an n-channel MOS transistor, the drain terminal is connected to one terminal of the fourth switch element SW4, the gate terminal is the first input-side transistor Ti1, and the first output The side transistors To1 to To3 are connected to the gate terminals of the third output side transistors To3, and the source terminals are connected to the ground line.

 That is, the first input side transistor Ti1 is an input side transistor by the first current source CS1, the first input side transistor Ti1, and the first output side transistor To1 to the fourth output side transistor To4. A current mirror circuit is configured with the output-side transistors To1 to To4 as output-side transistors. Here, in this embodiment, the electrical characteristics of the first output-side transistor To1 to the fourth output-side transistor To4 are set so as to generate currents corresponding to the corresponding bit data.

 Specifically, the first output-side transistor To1 corresponds to the bit data B1 of the first bit that is LSB in the 4-bit red gradation data DR, and is generated by the first current source CS1. The electrical characteristics are set so that 1/15 of the current Is is generated. The second output side transistor To2 corresponds to the bit data B2 of the second bit out of the 4-bit red gradation data DR, and is electrically generated so that 2/15 of the current Is is generated. Characteristics are set. The third output side transistor To3 corresponds to the bit data B3 of the third bit out of the 4-bit red gradation data DR and is electrically generated so that a current of 4/15 of the current Is is generated. Characteristics are set. The fourth output side transistor To4 corresponds to the bit data B4 of the 4th bit which is the MSB in the 4 bits of red gradation data DR, and a current of 8/15 of the current Is is generated. The electrical characteristics are set as follows.

 The first switch element SW1 corresponds to the bit data B1 of the first bit which is LSB in the 4-bit red gradation data DR, and the connection / disconnection between the two terminals according to the value of the bit data B1. One terminal of the switch element is connected to the drain terminal of the first output-side transistor To1, and the other terminal is connected to the input terminal of the second current source CS2. In the present embodiment, the connection is made when the bit data B1 is “1”, and the connection is not made when the bit data B1 is “0”.

 The second switch element SW2 corresponds to the bit data B2 of the second bit in the 4-bit red gradation data DR, and switches the connection / disconnection between the two terminals according to the value of the bit data B2. The element has one terminal connected to the drain terminal of the second output-side transistor To2, and the other terminal connected to the input terminal of the second current source CS2. In the present embodiment, the connection is made when the bit data B2 is “1”, and the connection is not made when the bit data B2 is “0”.

 The third switch element SW3 corresponds to the bit data B3 of the third bit in the red gradation data DR of 4 bits and switches the connection / disconnection between the two terminals according to the value of the bit data B3. The device has one terminal connected to the drain terminal of the third output-side transistor To3 and the other terminal connected to the input terminal of the second current source CS2. In this embodiment, connection is made when the bit data B3 is “1”, and connection is made when the bit data B3 is “0”.

 The fourth switch element SW4 corresponds to the bit data B4 of the fourth bit which is the MSB in the 4-bit red gradation data DR, and the connection / disconnection between the two terminals according to the value of the bit data B4. One terminal of the switching element is connected to the drain terminal of the fourth output-side transistor To4, and the other terminal is connected to the input terminal of the second current source CS2. In the present embodiment, connection is made when the bit data B4 is “1”, and connection is made when the bit data B4 is “0”.

 The second current source CS2 is a variable gain type constant current source that receives the threshold current command voltage Vapc1 and generates a threshold current Ith (= H2 · Vapc1) that is a product of the threshold current command voltage Vapc1 and the coefficient H2. The input terminal is connected to the other terminals of the first switch element SW1 to the fourth switch element SW4, the drain terminal and the gate terminal of the second input side transistor Ti2, and the output terminal is connected to the ground line. Yes.

 The second input side transistor Ti2 is a p-channel MOS transistor, the source terminal is connected to the power supply line Vcc, the gate terminal is connected to the drain terminal and the gate terminal of the fifth output side transistor To5, and the drain terminal Is connected to the input terminal of the second current source CS2 and the other terminals of the first switch element SW1 to the fourth switch element SW4.

 The fifth output-side transistor To5 is a p-channel MOS transistor, the source terminal is connected to the power supply line Vcc, the gate terminal is connected to the gate terminal and drain terminal of the second input-side transistor Ti2, and the drain terminal Is connected to the anode terminal of the red laser diode 30R.

 That is, the second input side transistor Ti2 and the fifth output side transistor To5 constitute a current mirror circuit in which the second input side transistor Ti2 is the input side and the fifth output side transistor To5 is the output side. The addition current of the threshold current Ith generated by the second current source CS2 and the current flowing through the other terminals of the first switch element SW1 to the fourth switch element SW4 (grayscale current Id) is input. A current having substantially the same current value as the current is output to the red laser diode 30R as a laser drive current IR.

 FIG. 4 is a laser characteristic diagram showing the relationship between the laser light amount of the red laser diode 30R and the laser drive current IR. As shown in FIG. 4, when the laser drive current IR is less than or equal to the threshold current Ith, the amount of laser light is very weak. The amount of laser light increases in proportion to the current value (gradation current Id).

 Specifically, for example, when the red gradation data DR is the gradation value “0”, that is, when the bit data B1 to B4 are all “0”, the first switch element SW1 to the fourth switch element SW4 are Since all are in a disconnected state, the gradation current Id = 0 and the laser drive current IR = Ith. In this case, as shown in FIG. 4, no laser light is generated in the red laser diode 30R (that is, black display). Further, when the red gradation data DR is the gradation value “1”, that is, when the bit data B1 is “1” and B2 to B4 are “0”, only the first switch element SW1 is connected. Current Id = Is / 15, and laser drive current IR = Ith + Is / 15. In this case, in the red laser diode 30R, a laser beam having a light amount corresponding to the gradation current Id = Is / 15 obtained by subtracting the threshold current Ith from the laser drive current IR is generated.

 Further, when the red gradation data DR is the gradation value “2”, that is, when the bit data B2 is “1” and B1, B3, and B4 are “0”, only the second switch element SW2 is connected. The gradation current Id = 2 · Is / 15, and the laser drive current IR = Ith + 2 · Is / 15. In this case, in the red laser diode 30R, a laser beam having a light amount corresponding to the gradation current Id = 2 · Is / 15 obtained by subtracting the threshold current Ith from the laser drive current IR is generated.

Thus, every time the gradation value increases by “1”, the laser drive current IR increases by Is / 15, and when the maximum gradation value is “15”, that is, all the bit data B1 to B4 are “1”. In this case, since the first switch element SW1 to the fourth switch element SW4 are all connected, the gradation current Id = Is and the laser drive current IR = Ith + Is. In this case, as shown in FIG. 4, in the red laser diode 30R, a laser beam having a light amount (a light amount corresponding to the maximum gradation value) corresponding to the gradation current Id = Is obtained by subtracting the threshold current Ith from the laser driving current IR. Will occur.
That is, the gradation current Id depends not only on the gradation current command voltage Vapc2 but also on the gradation value D indicated by the red gradation data DR, and therefore can be expressed as Id = H1 · Vapc2 · D.

 By the way, as can be seen from FIG. 4, the laser characteristics are temperature-dependent, and the threshold current Ith changes with temperature changes. In addition, the slope of the laser characteristic (amount of light change ΔP with respect to the amount of current change ΔI) also changes with temperature. Hereinafter, the slope of the laser characteristic is expressed as differential efficiency η (= ΔP / ΔI). That is, although details will be described later, in order to perform light amount correction in accordance with changes in laser characteristics, the threshold current Ith and the differential efficiency η may be corrected.

The above is the description of the red laser driver 20R, and the following description will be given returning to FIG. The green laser driver (drive signal generating means) 20G receives the green gradation data DG, the threshold current command voltage Vapc1 and the gradation current command voltage Vapc2 output from the correction system circuit block (not shown) for green. The laser drive current IG corresponding to the green gradation data DG is generated using the threshold current command voltage Vapc1 and the gradation current command voltage Vapc2, and output to the green laser diode 30G. The blue laser driver (driving signal generation means) 20B receives the blue gradation data DB, the threshold current command voltage Vapc1 and the gradation current command voltage Vapc2 output from the blue correction system circuit block (not shown). Using the threshold current command voltage Vapc1 and the grayscale current command voltage Vapc2, a laser drive current IB corresponding to the blue grayscale data DB is generated and output to the blue laser diode 30B.
The detailed configuration of the green laser driver 20G and the blue laser driver 20B is the same as that of the red laser driver 20R shown in FIGS.

 The red laser diode (light source) 30R generates a red single-color laser beam LR in accordance with the laser drive current IR supplied from the red laser driver 20R, and aligns the laser beam LR on the optical axis LA. Irradiation toward the optical system 40 (specifically, the first dichroic mirror 40a). In this embodiment, as shown in FIG. 1, the direction substantially parallel to the horizontal plane is set as the X axis, the direction orthogonal to the X axis in the horizontal plane is set as the Y axis, and the direction substantially perpendicular to the horizontal plane (XY plane) is set as the Z axis. The optical axis LA is set substantially parallel to the X axis. The outgoing optical axis of the laser beam LR coincides with the optical axis LA.

  The green laser diode (light source) 30G generates a green monochromatic laser beam LG according to the laser drive current IG supplied from the green laser driver 20G, and the optical system 40 for optical axis alignment (specifically, the laser beam LG). Irradiation along the Y-axis toward the first dichroic mirror 40a). The blue laser diode (light source) 30B generates a green laser beam LB in accordance with the laser drive current IB supplied from the blue laser driver 20B, and the optical axis alignment optical system 40 (in detail, the laser beam LB). Irradiation is performed along the Y axis toward the second dichroic mirror 40b).

  The optical axis alignment optical system 40 is an optical system for aligning the optical axes of the laser beams LR, LG, and LB, and includes a first dichroic mirror 40a and a second dichroic mirror 40b. The first dichroic mirror 40a is installed on the optical axis LA with an inclination of 45 ° with respect to the optical axis LA, and directs the laser beam LR toward the second dichroic mirror 40b along the optical axis LA. On the other hand, the laser beam LG is reflected toward the second dichroic mirror 40b so as to coincide with the optical axis LA. The second dichroic mirror 40b is installed on the optical axis LA with an inclination of 45 ° with respect to the optical axis LA, and the laser light LR and the laser light LG are transmitted to the laser scanning unit 50 along the optical axis LA. The laser beam LB is reflected toward the laser scanning unit 50 so as to coincide with the optical axis LA.

 The laser scanning unit (scanning unit) 50 is a resonance type MEMS (Micro Electro Mechanical System) scanner, and is incident on the optical axis alignment optical system 40 based on a scanning driving signal input from the scanning driving unit 60. The laser beams LR, LG, and LB to be scanned are scanned on the screen 100. Hereinafter, a detailed configuration of the laser scanning unit 50 will be described.

 FIG. 5 is a schematic configuration diagram of a laser scanning unit 50 which is a MEMS scanner. As shown in FIG. 5, the laser scanning section 50 includes a reflection mirror 50a, a first torsion spring 50b, an inner frame part 50c, a second torsion spring 50d, and an outer frame part 50e. The reflecting mirror 50a, the first torsion spring 50b, the inner frame portion 50c, the second torsion spring 50d, and the outer frame portion 50e are integrally formed by finely processing a semiconductor material such as single crystal silicon. It is.

 The reflection mirror 50a is a plate-like object having a reflection film formed on the reflection surface side so as to reflect the laser beams LR, LG, and LB toward the screen 100, and has a first axis AX1 (XY surface) along the reflection surface. Is a horizontal plane, it is connected to the inner frame part 50c by a first torsion spring (first rotation support part) 50b provided along the horizontal plane. That is, the reflecting mirror 50a is supported by the first torsion spring 50b so as to be rotatable about the first axis AX1. The shape of the reflection mirror 50a may be a square as shown in FIG. 5, or may be a circle or an ellipse.

 The inner frame portion 50c is a frame-shaped plate-like object, and is connected to the reflection mirror 50a by a first torsion spring 50b, along the reflection surface, and substantially perpendicular to the first axis AX1. 2 is connected to the outer frame part 50e by a second torsion spring (second rotation support part) 50d provided along an axis AX2 (when the XY plane is a horizontal plane, substantially parallel to the horizontal plane). That is, the inner frame portion 50c (reflection mirror 50a) is supported by the second torsion spring 50d so as to be rotatable around the second axis AX2. The outer frame part 50e is a frame-shaped plate-like object, and is connected to the inner frame part 50c by a second torsion spring 50d and to a fixed part (not shown). In this embodiment, since the optical axis LA is set to be parallel to the X axis, when the second axis AX2 is set to be parallel to the X axis, the laser beams LR, LG, and LB are set to the outer frame portion. The light is shielded by the light 50e and does not enter the reflection mirror 50a. In order to prevent this, in the present embodiment, as shown in FIG. 5, the laser scanning unit 50 is arranged so that the second axis AX2 has an inclination φ with respect to the optical axis LA (X axis).

 The laser scanning unit 50 having such a configuration scans the laser beams LR, LG, and LB in the X-axis direction on the screen 100 (that is, horizontal scanning) by rotating the reflection mirror 50a around the first axis AX1. In addition, the laser beam LR, LG, and LB is scanned in the Z-axis direction on the screen 100 (that is, vertical scanning) by rotating the reflection mirror 50a (inner frame portion 50c) about the second axis AX2. . The driving method for rotating the reflecting mirror 50a is generated by applying a voltage signal as a scanning drive signal to an electrode arranged at a predetermined position as described in Japanese Patent Application Laid-Open No. 2007-47354. A method using an electrostatic force may be employed, or in addition, a permanent magnet is provided to form a magnetic field, and a current signal is supplied as a scanning drive signal to a coil provided on the reflection mirror 50a or the inner frame 50c. You may employ | adopt the system using the Lorentz force to do. Since the driving method of the reflection mirror 50a in such a MEMS scanner is a known technique, a detailed description thereof will be omitted.

 Referring back to FIG. 1, the scanning driving unit 60 receives the synchronization signals (vertical synchronization signal Vsync and horizontal synchronization signal Hsync) as input, and the laser scanning unit based on the vertical synchronization signal Vsync and horizontal synchronization signal Hsync. A scanning drive signal for rotationally driving the 50 reflecting mirrors 50 a is generated and output to the laser scanning unit 50.

 The irradiation position detection unit 70 detects the irradiation positions of the laser beams LR, LG, and LB on the screen 100, and includes a horizontal angle sensor 70a, a vertical angle sensor 70b, and a timing signal generation circuit 70c. The horizontal angle sensor 70a detects the rotation angle θ1 around the first axis AX1 of the reflection mirror 50a, and outputs a horizontal angle detection signal indicating the rotation angle θ1 to the timing signal generation circuit 70c. The vertical angle sensor 70b detects the rotation angle θ2 around the second axis AX2 of the reflection mirror 50a, and outputs a vertical angle detection signal indicating the rotation angle θ2 to the timing signal generation circuit 70c. The horizontal angle sensor 70a and the vertical angle sensor 70b detect the angle by irradiating the back surface of the reflection mirror 50a (the surface opposite to the laser light reflection surface) and receiving the light reflected by the back surface. An optical angle sensor is used.

As shown in FIG. 6, the rotation angle θ1 detected by the horizontal angle sensor 70a is an angle of the reflection mirror 50a with respect to the Y axis in the XY plane. Further, as shown in FIG. 6, when a position X apart from the center point C0 of the screen 100 having the width W in the X-axis direction is a laser beam irradiation position Q, the coordinate Qx of the irradiation position Q in the horizontal scanning direction. Can be expressed as a function of the rotation angle θ1 if the distance d between the reflecting mirror 50a and the screen 100 is known. On the other hand, the rotation angle θ2 detected by the vertical angle sensor 70b is the angle of the reflection mirror 50a with respect to the Y axis in the YZ plane, and the coordinate Qy of the irradiation position Q in the vertical scanning direction is expressed as a function of the rotation angle θ2.
That is, the irradiation position Q (Qx, Qy) can be uniquely determined by detecting the rotation angle θ1 and the rotation angle θ2 of the reflection mirror 50a.

 The timing signal generation circuit 70c generates a pulsed scanning timing signal St that defines the start and end of one horizontal scanning period based on the horizontal angle detection signal indicating the rotation angle θ1, and the video signal processing circuit 10 and This is output to the pixel synchronous clock generation circuit 80. Further, the timing signal generation circuit 70c generates a pulse-like frame timing signal Ft for defining the start of one frame based on the vertical angle detection signal indicating the rotation angle θ2 and outputs it to the video signal processing circuit 10. To do.

 Specifically, the timing signal generation circuit 70 includes a start position and an end position of one horizontal scanning period based on the above-described unique relationship between the rotation angle θ1 and rotation angle θ2 of the reflection mirror 50a and the irradiation position Q. And a rotation angle θ2 corresponding to the irradiation position Q corresponding to the start position of one frame is set in advance, and the timing signal generation circuit 70 receives the horizontal angle detection signal. Is output when the rotation angle θ1 indicated by is coincident with the preset rotation angle θ1, and when the rotation angle θ2 indicated by the vertical angle detection signal coincides with the preset rotation angle θ2. A frame timing signal Ft is output.

 The pixel synchronization clock generation circuit 80 receives the scanning timing signal St, and based on the scanning timing signal St, a pulse shape that defines the irradiation timing of the laser light LR, LG, and LB corresponding to each pixel in one horizontal scanning period. The pixel synchronization clock signal CL is generated and output to the video signal processing circuit 10 and the light amount correction circuit 93. The pixel synchronization clock signal CL is output to the light amount correction circuit of the correction system circuit block corresponding to each color.

 The photoelectric conversion element 90 is, for example, a photodiode, and is arranged with the light receiving surface facing the optical axis LA, and outputs a current signal corresponding to the amount of laser light LR to the I / V converter 91. The I / V converter 91 converts the current signal input from the photoelectric conversion element 90 into a voltage signal and outputs the voltage signal to the A / D converter 92. The A / D converter 92 converts the voltage signal input from the I / V converter 91 into digital data (light quantity measurement data) Dpd and outputs the digital data to the light quantity correction circuit 93.

Here, in describing the detailed configuration of the light amount correction circuit (light amount correction means) 93, the principle of light amount correction in the present embodiment, which is the premise thereof, will be described.
Now, the target light quantity T is represented as T = M · D, and the actual laser light quantity P is represented as P = a · D + b. Here, D is a gradation value indicated by gradation data of each color, M is a coefficient, a and b are variables (a is a first variable, and b is a second variable).

As shown in FIG. 7 (a), the target light amount _{T k} corresponding to a certain gray scale value _{D k,} the amount of laser light and _{P k,} the difference between _{P k} and _{T k} is represented by the light amount error [delta] _k . It is a basic idea of the amount of light correction in the present embodiment for setting the threshold current command value Dapc1 and the gradation current command value Dapc2 to minimize the light amount error [delta] _k.

 FIG. 7B shows a case where the laser characteristic is changed and the variable b of the laser light quantity P is increased. FIG. 7C is a case where the laser characteristic is changed and the variable b of the laser light quantity P is reduced. FIG. 7D shows the case where the laser characteristic is changed and the variable a of the laser light quantity P is increased, and FIG. 7E is the case where the laser characteristic is changed and the variable a of the laser light quantity P is reduced. It is shown. Since the variable b is a variable corresponding to the threshold current Ith and the variable a is a variable corresponding to the differential efficiency η, the threshold current Ith is corrected in the cases of FIGS. 7B and 7C, and FIG. ) And (e), it is understood that the differential efficiency η should be corrected. That is, the threshold current Ith is corrected by the threshold current command value Dapc1, and the differential efficiency η is corrected by the gradation current command value Dapc2.

 As described above, in order to set the threshold current command value Dapc1 and the gradation current command value Dapc2, the light amount error δ () between the target light amount T corresponding to a certain gradation value D and the actually measured laser light amount P. = P−T) needs to be measured, but if the number of times of measurement is small, inaccuracy of the set value due to a measurement error occurs. Therefore, it is desirable to increase the number of times of measurement and sequentially improve the measurement accuracy. In the present embodiment, the least square method using the steepest descent method capable of sequentially and rapidly searching for the minimum value of the sum of squares of the light amount error δ is used.

Here, by setting the gray scale value D, when the procedure was repeated to measure the laser light amount P to k-th tone value _{{D 1, D 2, ··} , D i, ··, D k} for the laser light quantity _{{P 1, P 2, ··} , P i, ··, P k}, the target light amount _{{T 1, T 2, ··} , T i, ··, T k} and. The evaluation function ε _k is expressed as the sum of squares of the light amount error as in the following formula (1), and variables a and b that minimize the evaluation function ε _k are sequentially obtained for each i. When the steepest descent method in which the inclinations due to changes in the variables a and b are obtained and a and b are corrected in the directions is used, a _k and b _k can be expressed by the following equations (2) and (3). In the following formulas (2) and (3), μa and μb are coefficients.

In the above equation (2), ∂ε _k / ∂a is represented by the following equation (4), and in the above equation (3), ∂ε _k / ∂b is represented by the following equation (5). Accordingly, the following expression (6) is derived from the expressions (2) and (4), and the following expression (7) is derived from the expressions (3) and (5). Furthermore, if it deform | transforms so that it can calculate sequentially, the following (8) Formula-(12) Formula will be obtained.

 Since the variable b is a variable corresponding to the threshold current Ith and the variable a is a variable corresponding to the differential efficiency η, the differential efficiency η is the product of the light amount error and the gradation value as shown in the above equation (10). It is understood that the threshold current Ith may be corrected by the integrated value of the light quantity error as shown in the above equation (12).

Now, a method for converting the above-described principle into a circuit will be described below.
First, the above method is illustrated in FIG. The laser driver from the DA converters 94 and 95 to the AD converter 92, the laser diode, the photoelectric conversion element 90, and the like are controlled objects 400, and the threshold current command value Dapc1 and the gradation current command value Dapc2 from the laser light quantity P and the gradation value D. Will be calculated.

 Here, the control object 400 will be described. Laser drive current I, laser light quantity W, output current Ipd of photoelectric conversion element 90, output voltage VL of I / V converter 91, output value P of A / D converter 92, threshold current command voltage Vapc1, gradation current command The voltage Vapc2 is expressed as the following formulas (13) to (19). In the following formulas (13) to (19), H1, H2, F, Kpd, R, Gad, and Gda are coefficients.

By sequentially substituting other formulas into the formula (17), the following formula (20) is obtained. On the other hand, since it is defined as P = a · D + b as described above, the variable a is expressed by the following equation (21) from the equation (20), and the variable b is expressed by the following equation (22). That is, by transforming Equation (21), Equation (23), which is a conversion equation for converting the corrected _ak into the gradation current command value Dapc2 in the conversion element 406, is obtained. Further, by transforming equation (22), equation (24), which is a conversion equation for converting b _k after correction into threshold current command value Dapc1, is obtained in conversion element 409.

 When attention is paid to the part for calculating the threshold current command value Dapc1, an error integrating element 407, a correction element 408 and a variable conversion element 409 are connected in series as shown in FIG. If this is represented as a block diagram using the delay elements 410 and 411, it is as shown in FIG. The delay element 410 performs error accumulation, and the delay element 411 sequentially corrects the parameter b. In order to simplify this block diagram, equation (11) is transformed into equation (25). When b in Expression (25) is converted into a variable by Expression (26), Expression (27) is obtained. When Expression (27) is expressed in a block diagram, the result is as shown in FIG. 9C, and the output of the delay element 410 is multiplied by μb / K by the gain element 413 and sent to the delay element 412. Equivalent behavior.

Now, since the delay element is realized by a flip-flop, it is necessary to prevent the operation from being lost. For this purpose, an arithmetic unit for gain adjustment is inserted in each place and the delay element is replaced with a flip-flop as shown in FIG. 9D. In order for the operations shown in FIGS. 9C and 9D to be equivalent, each gain only needs to satisfy the relationship of Expression (28). The output of the flip-flop 414 is a variable scaled Sa _k, a, the output of flip-flop 415 is a variable using a variable convert b _k, since complicated, and subsequently expressed as Sb _k and b _k May explain.

  Next, attention will be focused on the part for calculating the gradation current command value Dapc2 in FIG. When this portion is extracted, as shown in FIG. 10A, the error integrating element 404, the correcting element 405, and the variable converting element 406 are connected in series. If a delay element is used and expressed in a block diagram, the result is as shown in FIG. As can be seen from this figure, the gain element 420 is moved, and the operation between the input and output does not change as shown in FIG. This corresponds to transforming equation (9) into equation (29) and replacing the variable with equation (30) to form equation (31).

Now, if gains are inserted in various places as before and the delay elements are replaced with flip-flops, FIG. 10D is obtained. Here, the gain element 426 is inserted for gain adjustment for circuit sharing. If each gain satisfies Expression (32), FIGS. 10C and 10D are equivalent to each other. The output of flip-flop 427 is a variable scaled Sa _k, a, the output of flip-flop 428 is a variable scaling a _k, since complicated, and subsequently expressed as Sa _k and b _k Description There is a case.

 Based on the principle of light quantity correction in the present embodiment as described above, the detailed configuration of the light quantity correction circuit 93 will be described below with reference to FIG. As shown in FIG. 11, the light quantity correction circuit 93 includes an initial setting circuit 300, an M multiplier 301, a subtractor 302, a multiplier 303, a G7 divider 304, a G3 divider 305, an adder 306, flip-flops 307, and G2. Divider 308, subtractor 310, flip-flop 311, G1 divider 312, G6 divider 314, adder 315, flip-flop 316, G5 divider 317, subtractor 319, flip-flop 320, G4 subtractor 321, G1 multiplication And a G4 multiplier 324.

Initialization circuit 300, at or reset at power-on of the image display device LSD, on the basis of the light amount measurement value _{P i} indicated light amount measurement data Dpd, adjusts the threshold current command value Dapc1 and the gradation current command value Dapc2 Thus, a predetermined initial setting operation is performed. Further, the initial setting circuit 300 has a function of outputting gradation data DR, DG, DB of each color used during the initial setting operation to the laser drivers 20R, 20G, 20B of each color. Details of this initial setting operation will be described later.

The M multiplier 301 outputs the product of the gradation value D _i indicated by the gradation data DR, DG, and DB of each color and the coefficient M to the subtracter 302 as the target light amount T _i (= M · D _i ). Subtractor 302 outputs a value obtained by subtracting the target amount _{T i} from light amount measurement value _{P i,} the light amount error _{δ i (= P i -T i} ) as a multiplier 303 and G6 divider 314.

Multiplier 303 outputs the product of tone value D _i and light amount error δ _i (hereinafter referred to as moment MT _i ) to G7 divider 304. The G7 divider 304 outputs a value obtained by dividing the moment MT _i by the coefficient G7 to the G3 divider 305. The G3 divider 305 outputs a value obtained by dividing the output value (MT _i / G7) of the G7 divider 304 by the coefficient G3 to the adder 306.

The adder 306 outputs the addition value of the output value of the G3 divider 305 (MT _i / (G7 · G3)) and the output value of the flip-flop 307 to the D input terminal of the flip-flop 307. The flip-flop 307 is a D-type flip-flop, and reflects the input value of the D input terminal as an output value in synchronization with the pixel synchronization clock signal CL. That is, the adder 306 and the flip-flop 307 constitute an integration circuit for the moment MT _i (= δ _i · D _i ), and the output value of the flip-flop 307 becomes the integration value of the moment MT _i . Below, the cumulative value of this moment MT _i and Sa _k. Sa _k = δ ₁ · D ₁ + ·· + δ _i · D _i + ·· + δ _k · D _k .

G2 divider 308 outputs a value obtained by dividing the integrated value Sa _k moment MTi by a factor G2 to the subtracter 310. The subtractor 310 outputs a value obtained by subtracting the output value (= Sa _k / G2) of the G2 divider 308 from the output value of the flip-flop 311 to the D input terminal of the flip-flop 311. The flip-flop 311 is a D-type flip-flop, and reflects the input value of the D input terminal as an output value in synchronization with the pixel synchronization clock signal CL. Here, as the initial output value a _k−1 of the flip-flop 311, a value obtained by multiplying the gradation current command value Dapc2 initialized by the initial setting circuit 300 by the coefficient G1 by the G1 multiplier 323 is loaded. Yes. In other words, the subtractor 310 and the flip-flop 311, (9) correction circuit for calculating the _{a k = a k-1 -μa} · Sa k of the formula is configured, the output value of the flip-flop 311 a _k .

The G1 divider 312 outputs a value obtained by dividing the output value _ak of the flip-flop 311 by the coefficient G1 to the D / A converter 95 as the gradation current command value Dapc2.

The G6 divider 314 outputs a value obtained by dividing the light amount error δ _i by the coefficient G6 to the adder 315. Adder 315 outputs the addition value of the output value of G6 divider 314 (= δ _i / G6) and the output value of flip-flop 316 to the D input terminal of flip-flop 316. The flip-flop 316 is a D-type flip-flop, and reflects the input value of the D input terminal as an output value in synchronization with the pixel synchronization clock signal CL. That is, the adder 315 and the flip-flop 316 constitute an integration circuit for the light amount error δ _i , and the output value of the flip-flop 316 is an integrated value of the light amount error δ _i . Hereinafter, the integrated value of the light quantity error δ _i is Sb _k . Note that Sb _k = δ ₁ + ·· + δ _i + ·· + δ _k .

The G5 divider 317 outputs, to the subtractor 319, a value obtained by dividing the integrated value of the light amount error δ _i by Sb _k by the coefficient G5. The subtractor 319 outputs a value obtained by subtracting the output value (= Sb _k / G5) of the G5 divider 317 from the output value of the flip-flop 320 to the D input terminal of the flip-flop 320. The flip-flop 320 is a D-type flip-flop, and reflects the input value of the D input terminal as an output value in synchronization with the pixel synchronization clock signal CL. Here, as the initial output value b _k−1 of the flip-flop 320, a value _obtained by multiplying the threshold current command value Dapc1 initialized by the initial setting circuit 300 by the coefficient G4 by the G4 multiplier 324 is loaded. . That is, the subtractor 319 and the flip-flop 320 constitute a correction circuit that calculates b _k = b _k−1 −μb · Sb _k expressed by the above equation (11), and the output value of the flip-flop 320 is b _k .

The G4 divider 321 outputs a value obtained by dividing the output value b _k of the flip-flop 320 by the coefficient G4 to the D / A converter 94 as a threshold current command value Dapc1.
By providing the G7 divider 304, it becomes possible to set G3 = G6, G2 = G5, G1 = G4, and the circuit can be shared and the circuit scale can be reduced.

The above is the description of the light amount correction circuit 93. The following description will be given with reference again to FIG.
The D / A converter 94 converts the threshold current command value Dapc1 input from the light amount correction circuit 93 described above into a threshold current command voltage Vapc1 (= Gda · Dpc1), and outputs it to the red laser driver 20R. The D / A converter 95 converts the gradation current command value Dapc2 input from the above-described light amount correction circuit 93 into a gradation current command voltage Vapc2 (= Gda · Dpc2), and outputs it to the red laser driver 20R.
In the above description, the correction system circuit block for red is used as a representative, but the same applies to the correction system circuit blocks for green and blue.

 The screen 100 is a transmissive screen that transmits the laser beams LR, LG, and LB scanned by the laser scanning unit 50. That is, this image display apparatus LSD is a rear projection type projector, and the user views the display image from the surface opposite to the irradiation surface of the laser light LR, LG, and LB on the screen 100. Although not shown in FIG. 1, the image display apparatus LSD exposes only the viewing side surface of the screen 100, and other components are housed inside the housing, and are influenced by external light. It is the structure which excludes.

  Next, the operation of the image display device LSD in the present embodiment configured as described above will be described. In the following description, the correction system circuit block for red is used as a representative, but the same applies to the correction system circuit blocks for green and blue.

(Initial setting operation at power-on)
First, an initial setting operation by the initial setting circuit 300 of the light amount correction circuit 93 when the power is turned on will be described. FIG. 12 is a characteristic diagram showing a correspondence relationship between Dpd (that is, the red laser light amount actual measurement value P) that is the output of the A / D converter 92 and the laser drive current. As shown in FIG. 12, the characteristic curve itself has the same shape as that in FIG. 4, but it can be seen that an offset occurs in Dpd due to the offset of the I / V converter 91. The initial setting operation of the initial setting circuit 300 when the power is turned on is performed to correct the offset superimposed on the Dpd.

  FIG. 13 is a flowchart showing an initial setting operation by the initial setting circuit 300 of the light amount correction circuit 93. First, in order to completely turn off the red laser diode 30R, the initial setting circuit 300 sets the threshold current command value Dapc1 = 0 and the grayscale current command value Dapc2 = 0 and displays the grayscale value D = 0. The tone data DR is output to the red laser driver 20R (step S1). As a result, the laser drive current IR supplied from the red laser driver 20R to the red laser diode 30R becomes completely zero, and the red laser diode 30R is completely turned off. At this time, the initial setting circuit 300 acquires the Dpd input from the A / D converter 92 as the measured value Dpd0 of the black level (step S2).

  Subsequently, the initial setting circuit 300 increases the threshold current command value Dapc1 by the first unit amount (step S3), and acquires Dpd at this time (step S4). Then, the initial setting circuit 300 determines whether or not the value of Dpd−Dpd0 is larger than the set light amount 1 set in the obvious light emission state as shown in FIG. 12 (step S5). Returning to step S3, the processes of steps S3 to S5 are repeated.

  On the other hand, if “YES” in step S5, that is, if Dpd−Dpd0> the set light amount 1, the initial setting circuit 300 decreases the threshold current command value Dapc1 by the second unit amount (step S6), and acquires Dpd at this time (Step S7). Then, the initial setting circuit 300 determines whether or not the conditions of Dpd−Dpd0> set light amount 2−allowable error and Dpd−Dpd0 <set light amount2 + allowable error are satisfied (step S8). Returning to step S6, the processes of steps S6 to S8 are repeated. Here, the set light quantity 2 is set to a value that is regarded as a black level as shown in FIG.

On the other hand, if “YES” in step S8, the initial setting circuit 300 sets the value of Dapc1 at that time as the initial value of the threshold current command value Dapc1 (step S9). At the same time, the initial setting circuit 300 outputs the initial value of the threshold current command value Dapc1 to the G4 multiplier 324, and the value obtained by multiplying the initial value of the threshold current command value Dapc1 by the coefficient G4 by the G4 multiplier 324 is flip-flops. Is loaded into the flip-flop 320 as the initial output value b _k−1 of the loop 320.

  Subsequently, the initial setting circuit 300 outputs the red gradation data DR indicating the gradation value D = 15 (that is, the maximum gradation value) to the red laser driver 20R (Step S10), and the gradation current command value Dapc2 is output. The unit amount is increased by 3 (step S11), and Dpd at this time is acquired (step S12). Then, the initial setting circuit 300 determines whether or not the conditions of Dpd−Dpd0> set light amount 3−allowable error and Dpd−Dpd0 <set light amount 3 + allowable error are satisfied (step S13). Returning to step S10, the processes of steps S10 to S13 are repeated. Here, the set light amount 3 is set to the target value of the maximum light emission amount as shown in FIG.

On the other hand, if “YES” in step S13, the initial setting circuit 300 sets the value of Dapc2 at that time as the initial value of the gradation current command value Dapc2 (step S14). At the same time, the initial setting circuit 300 outputs the initial value of the gradation current command value Dapc2 to the G1 multiplier 323, and a value obtained by multiplying the initial value of the threshold current command value Dapc2 by the coefficient G1 by the G1 multiplier 323 is obtained. The initial output value a _k−1 of the flip-flop 311 is loaded into the flip-flop 311. By the initial setting operation as described above, the initial value of the threshold current command value Dapc1 and the initial value of the gradation current command value Dapc2 in which the offset superimposed on Dpd is corrected are set.
Note that the above-described initial setting operation is similarly performed in the correction circuit blocks for green and blue.

(Steady operation)
Next, the operation of the image display device LSD during normal operation will be described with reference to the timing chart of FIG.
Here, a video signal and a synchronization signal (vertical synchronization signal Vsync and horizontal synchronization signal Hsync) have already been input from an external image supply device, and the video signal processing circuit 10 should display based on the video signal and the synchronization signal. It is assumed that digital gradation data defining gradation values corresponding to each pixel of the image is generated, and the digital gradation data is stored in the internal memory in units of one frame.

 Further, the reflection mirror 50a of the laser scanning unit 50 starts rotating by the scanning drive signal output from the scanning driving unit 60 in response to the input of the synchronization signal, and the rotation angle θ2 of the reflection mirror 50a with respect to the vertical scanning direction is set at time t1. It coincides with the angle corresponding to the start position of one frame on the screen 100, and at time t2, the rotation angle θ1 of the reflection mirror 50a with respect to the horizontal scanning direction corresponds to the start position of one horizontal scanning period on the screen 100. Assume that it matches the angle. That is, the frame timing signal Ft that defines the start of one frame is output from the timing signal generation circuit 70c at time t1, and the scan timing signal St that defines the start of one horizontal scanning period is output at time t2. Furthermore, it is assumed that the rotation angle θ1 of the reflection mirror 50a with respect to the horizontal scanning direction coincides with the angle corresponding to the end position of one horizontal scanning period on the screen 100 at time t3. That is, the scanning timing signal St defining the end of one horizontal scanning period is output from the timing signal generating circuit 70c at time t3.

 At such a time t2, when the scanning timing signal St defining the start of one horizontal scanning period is input to the pixel synchronous clock generation circuit 80, the laser light LR, LG corresponding to each pixel in one horizontal scanning period and A pixel synchronization clock signal CL that defines the LB irradiation timing is generated and output to the video signal processing circuit 10 and the light amount correction circuit 93. As described above, the rotation angle θ1 in one horizontal scanning period, that is, the irradiation position Qx is uniquely related to the time elapsed from the start of one horizontal scanning period, and naturally corresponds to each pixel in one horizontal scanning period. The irradiation position Qx to be performed and the elapsed time are uniquely related. Therefore, in the present embodiment, as shown in FIG. 14, scanning that defines the start of one horizontal scanning period based on a unique relationship between the irradiation position Qx corresponding to each pixel and the elapsed time in one horizontal scanning period. After the timing signal St is input, a pulsed pixel synchronization clock signal CL that defines the irradiation timing of the laser beams LR, LG, and LB corresponding to each pixel according to the elapsed time is generated.

 As can be seen from FIG. 14, the pulse interval of the pixel synchronization clock signal CL changes according to the irradiation position Qx, that is, the elapsed time. For example, the pulse interval is short near the time t13 to t17 near the center of the screen 100, and the pulse interval is long near both ends of the screen 100. This is because the changing speed (scanning speed) of the rotation angle θ1 of the reflection mirror 50a changes in a sine wave shape according to the elapsed time due to the characteristics of the laser scanning unit 50 which is a MEMS scanner.

On the other hand, when the frame timing signal Ft that defines the start of one frame and the scanning timing signal St that defines the start of one horizontal scanning period are input, the video signal processing circuit 10 receives the first frame of the internal memory. Read digital gradation data (red gradation data DR, green gradation data DG, blue gradation data DB) of each pixel corresponding to the horizontal scanning period of the first row from the storage area storing the digital gradation data. The red gradation data DR, the green gradation data DG, and the blue gradation data DB are sequentially output in synchronization with the pixel synchronization clock signal CL. Specifically, as shown in FIG. 14, when the first pixel synchronization clock signal CL is input at time t2, the video signal processing circuit 10 corresponds to the start position (first column) of one horizontal scanning period. The red gradation data DR for the red pixel is output to the red laser driver 20R and the light amount correction circuit 93.
In the following description, for convenience of explanation, the description will be made focusing on the red gradation data DR.

Here, the tone value indicated by the red gray-scale data DR that is input to the light amount correction circuit 93 and D _1, the light amount measured value indicated by the light amount measurement data Dpd outputted from the A / D converter 92 to the light amount correction circuit 93 It is referred to as _{P 1.} In this case, in the light amount correction circuit 93 shown in FIG. 11, the output value of the M multiplier 301 is T ₁ = M · D ₁ , and the output value of the subtractor 302 is δ ₁ = P ₁ −M · D ₁ . The output value of the device 303 is D ₁ · δ ₁ , the output value of the flip-flop 307 is Sa ₁ = D ₁ · δ ₁ , and the output value of the flip-flop 311 is a ₁ = a 0 (the initial value of the gradation current command value Dapc2 value) becomes a -μa · Sa _1. Such a ₁ is output to the D / A converter 95 as the gradation current command value Dapc2, converted into the gradation current command voltage Vapc2 by the D / A converter 95, and the first current of the red laser driver 20R. Output to source CS1.

On the other hand, the output value of the flip-flop 316 is Sb ₁ = δ ₁ , and the output value of the flip-flop 320 is b ₁ = b 0 (initial value of the threshold current command value Dapc ₁ ) −μb · Sb ₁ . Such b ₁ is output to the D / A converter 94 as the threshold current command value Dapc1, converted into the threshold current command voltage Vapc1 by the D / A converter 94, and the second current source CS2 of the red laser driver 20R. Is output.

As a result, the red laser driver 20R receives the red gradation data DR for the red pixel corresponding to the start position (first column) of one horizontal scanning period, the gradation current command voltage Vapc2, and the threshold current command voltage Vapc1. Is input, a laser drive current represented by IR = H 2 · Vapc 2 · D ₁ + H 1 · Vapc ₁ is generated and supplied to the red laser diode 30R. As a result, the red laser diode 30R generates laser light LR corresponding to the gradation value of the red pixel in the first column, and this laser beam LR is reflected by the reflecting mirror 50a in the first row of red pixels in one horizontal scanning period. The irradiation position Qx corresponding to is irradiated.

  Next, as shown in FIG. 14, when a pixel synchronization clock signal corresponding to the second column of one horizontal scanning period is generated at time t10, the video signal processing circuit 10 corresponds to the second column of one horizontal scanning period. The red gradation data DR for the red pixel to be output is output to the red laser driver 20R and the light amount correction circuit 93.

Here, the tone value indicated by the red gray-scale data DR that is input to the light amount correction circuit 93 and D _2, the light amount measured value indicated by the light amount measurement data Dpd outputted from the A / D converter 92 to the light amount correction circuit 93 It is referred to as _{P 2.} In this case, in the light amount correction circuit 93 shown in FIG. 11, the output value of the M multiplier 301 is T ₂ = M · D ₂ , and the output value of the subtracter 302 is δ ₂ = P ₂ −M · D ₂ . output value of the vessel 303 is _{D 2} · _{δ 2,} and an output value of the flip-flop 307 _Sa 2 = D
₁ · δ ₁ + D ₂ · δ ₂ , and the output value of the flip-flop 311 is a ₂ = a ₁ −μa · Sa ₂ . Such _{a 2} is output to the D / A converter 95 as the gradation current command value Dapc2, it is converted to the gradation current command voltage Vapc2 by the D / A converter 95, a first current of the red laser driver 20R Output to source CS1.

On the other hand, the output value of the flip-flop 316 is Sb ₂ = δ ₁ + δ ₂ , and the output value of the flip-flop 320 is b ₂ = b ₁ −μb · Sb ₂ . Such _{b 2} is output to the D / A converter 94 as the threshold current command value Dapc1, is converted to the threshold current command voltage Vapc1 by the D / A converter 94, a second current source of the red laser driver 20R CS2 Is output.

Thus, the red laser driver 20R receives the red gradation data DR for the red pixel corresponding to the second column of one horizontal scanning period, the gradation current command voltage Vapc2, and the threshold current command voltage Vapc1. Therefore, a laser driving current represented by IR = H 2 · Vapc ₂ · D ₂ + H 1 · Vapc 1 is generated and supplied to the red laser diode 30 R. Thereby, the red laser diode 30R generates laser light LR corresponding to the gradation value of the red pixel in the second column, and this laser beam LR is reflected by the reflecting mirror 50a in the second column of red pixels in one horizontal scanning period. The irradiation position Qx corresponding to is irradiated.

  Subsequently, as shown in FIG. 14, when a pixel synchronization clock signal corresponding to the third column of the one horizontal scanning period is generated at time t11, the video signal processing circuit 10 corresponds to the third column of the one horizontal scanning period. The red gradation data DR for the red pixel to be output is output to the red laser driver 20R and the light amount correction circuit 93.

Here, the tone value indicated by the red gray-scale data DR that is input to the light amount correction circuit 93 and D _3, the light amount measured value indicated by the light amount measurement data Dpd outputted from the A / D converter 92 to the light amount correction circuit 93 It is referred to as _{P 3.} In this case, in the light amount correction circuit 93 shown in FIG. 11, the output value of the M multiplier 301 is T ₃ = M · D ₃ , and the output value of the subtractor 302 is δ ₃ = P ₃ −M · D ₃ output value of the vessel 303 is _{D 3} · _{δ 3,} and an output value of the flip-flop 307 _Sa 3 = D
₁ · δ ₁ + D ₂ · δ ₂ + D ₃ · δ ₃ , and the output value of the flip-flop 311 is a ₃ = a ₂ -μa · Sa ₃ . Such _{a 3} is output to the D / A converter 95 as the gradation current command value Dapc2, it is converted to the gradation current command voltage Vapc2 by the D / A converter 95, a first current of the red laser driver 20R Output to source CS1.

On the other hand, the output value of the flip-flop 316 is Sb ₃ = δ ₁ + δ ₂ + δ ₃ , and the output value of the flip-flop 320 is b ₃ = b ₂ −μb · Sb ₃ . Such _{b 3} is output to the D / A converter 94 as the threshold current command value Dapc1, is converted to the threshold current command voltage Vapc1 by the D / A converter 94, a second current source of the red laser driver 20R CS2 Is output.

Thus, the red laser driver 20R receives the red gradation data DR for the red pixel corresponding to the third column of one horizontal scanning period, the gradation current command voltage Vapc2, and the threshold current command voltage Vapc1. Therefore, a laser drive current represented by IR = H 2 · Vapc 2 · D ₃ + H 1 · Vapc 1 is generated and supplied to the red laser diode 30R. Thus, the red laser diode 30R generates laser light LR corresponding to the gradation value of the red pixel in the third column, and this laser beam LR is reflected by the reflecting mirror 50a on the red pixel in the third column in one horizontal scanning period. The irradiation position Qx corresponding to is irradiated.
Thereafter, the same operation is repeated until the last column in one horizontal scanning period (corresponding to time t20 in FIG. 14), and an image in one horizontal scanning period from time t2 to t3 is displayed on the screen 100.

In FIG. 14, the period from time t4 to t5 represents the next (second row) one horizontal scanning period, the period from time t6 to t7 represents the third horizontal scanning period, and time t8 to t9. This period indicates one horizontal scanning period of the fourth row, and the same operation as described above is performed in each one horizontal scanning period, and one horizontal scanning period of the last row is completed, thereby completing one frame. Are displayed on the screen 100. Of course, every time one horizontal scanning period ends, the rotation angle θ2 of the reflecting mirror 50a in the vertical scanning direction changes to an angle corresponding to the next horizontal scanning period.
In the above description, the red gradation data DR has been described. However, the same light amount correction is performed on the green gradation data DG and the blue gradation data DB by the correction system circuit blocks corresponding to them. Is called.

  As described above, according to the image display device LSD according to the present embodiment, the variables a and b that minimize the light amount error that is the difference between the target light amount and the actually measured light amount are sequentially performed while performing the display operation. And a threshold current command value Dapc1 that can correct the threshold current Ith and a grayscale current command value Dapc2 that can correct the differential efficiency η based on the variables a and b. Light quantity correction according to changes in laser characteristics caused by temperature changes during operation can be performed in real time, and high light quantity correction accuracy can be obtained, so that display quality can be improved.

By the way, when the deviation of the laser light quantity actual measurement value P from the target light quantity T is in a state as shown in FIG. 15, the light quantity error integrated value Sb _k and the product (moment) of the light quantity error and the gradation value are integrated. value Sa _k is, becomes substantially zero, the phenomenon that the correction operation in the light quantity correction circuit 93 is stopped may occur. In order to prevent such a phenomenon, as shown in FIG. 16, the gradation value used for obtaining the moment is set to an intermediate value from the minimum gradation value to the maximum gradation value, so that the light amount error is increased. an integrated value Sa _k of the product (moment) of the tone values can be prevented from becoming substantially zero, it is possible to prevent the stop of the correction operation in the light quantity correction circuit 93.

Further, by sequentially calculating the average value of the gradation values and using this average value as the gradation value used when obtaining the moment, the product of the light amount error and the gradation value is obtained in the same manner as described above. can be integrated value Sa _k of (moment) is prevented from becoming substantially zero. If this is explained by an equation, an integrated value of the product of the difference between the gradation value D _k and the gradation average value D _ave and the light amount error is calculated as in Equation (33) instead of Equation (10). . In this case, as shown in FIG. 17, an averaging circuit 330 that sequentially calculates an average value of the gradation values Di in the previous stage of the multiplier 303, and an output value (gradation) of the averaging circuit 330 from the gradation values. A subtracter 331 for subtracting the (average value) may be provided. Further, not only the average value but also a preset value, for example, an 8-bit gradation expression can be used, the gradation value “128” may be used when obtaining the moment.

  In the above embodiment, the light amount correction is performed during the display operation. However, there is a possibility that the light amount correction cannot be performed normally if there is a bias in the gradation value, for example, if there is a very dark image. As a countermeasure against this, a video signal processing circuit is used during a period in which image display is not performed (a period in which laser light is not scanned on the screen 100), such as a period from time t3 to t4 shown in FIG. 14 or a period from time t5 to t6. 10 may generate a predetermined gradation value (gradation data) or a pseudo pixel synchronization clock signal to cause the laser diode to emit light, and the light amount correction circuit 93 may perform the light amount correction operation.

In the above embodiment, the integrated value Sb _k of light amount error, when calculating the integrated value Sa _k of the product (moment) of the light amount error and the gray scale value, the most recent data (the light amount error and the gray scale value Since it is desirable to emphasize the product value), the weight of past data may be lowered. Specifically, weighting constant multipliers may be provided in the feedback path from the output terminal of the flip-flop 307 to the adder 306 and the feedback path from the output terminal of the flip-flop 316 to the adder 315 shown in FIG. . This weighting constant is set to a value smaller than 1, for example 7/8. Thus, when calculating the integrated value Sb _k of light amount error, the integrated value Sa _k of the product (moment) of the light amount error and the gray scale values, for sequentially forgetting the past data, emphasis on the most recent data Can be put.
In the above embodiment, the integrated value Sb _k of light amount error, a value proportional to the integrated value Sa _k of the product (moment) of the light amount error and the gray scale values, are sequentially corrected variables a and b It was, but the integrated value Sb _k, the correction of the more constant value of the code of the integrated value Sa _k may be applied to the variable a and b.

  In the above embodiment, the laser scan display that scans the laser beam on the screen 100 to display an image has been described as an example. However, the present invention is not limited to this, and is generated from an LED (Light Emitting Diode) or other light source. The present invention can also be applied to an image display device that displays an image by scanning light. In the above embodiment, the laser scan display using one scanner for the three color laser diodes has been described as an example. However, the present invention is not limited to this, and a configuration may be adopted in which a scanner is provided for each color.

  In addition, the circuit configuration of the red laser driver 20R (green laser driver 20R, blue laser driver 20B) described with reference to FIG. 3 in the above embodiment may be changed as appropriate according to the maximum number of gradations. In other words, in the above embodiment, since the maximum number of gradations is assumed to be “16 (4 bits)”, four output side transistors (first output side transistor To1 to fourth output side) of the current mirror circuit in FIG. For example, when the maximum number of gradations is set to “256 (8 bits)”, it is sufficient to provide eight output-side transistors of the current mirror circuit (8 switch elements are also provided).

  In this case, the electrical characteristics of the output side transistor corresponding to the bit data of the first bit are set so that a current of 1/255 of the current Is is generated, and the output side transistor corresponding to the bit data of the second bit is set. Is set so that a current of 2/255 of the current Is is generated, and the electrical characteristic of the output side transistor corresponding to the bit data of the third bit is the current of 4/255 of the current Is. The electrical characteristics of the output side transistor corresponding to the bit data of the 4th bit are set so that 8/255 current of the current Is is generated, and the bit data of the 5th bit is set. The electrical characteristics of the corresponding output side transistor are set so that a current of 16/255 of the current Is is generated, and the output side transistor corresponding to the bit data of the 6th bit The electrical characteristics are set so that a current of 32/255 of the current Is is generated, and the electrical characteristics of the output-side transistor corresponding to the bit data of the seventh bit are generated as a current of 64/255 of the current Is. The electrical characteristics of the output side transistor corresponding to the bit data of the 8th bit may be set so that a current of 128/255 of the current Is is generated.

1 is a configuration block diagram of an image display device LSD according to an embodiment of the present invention. It is a block diagram of the red laser driver 20R in the image display device LSD according to an embodiment of the present invention. It is a circuit block diagram of the red laser driver 20R in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a laser characteristic figure of red laser diode 30R in image display device LSD concerning one embodiment of the present invention. It is the structure schematic of the laser scanning part 50 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is explanatory drawing regarding rotation angle (theta) 1 of the reflective mirror 50a which the horizontal angle sensor 70a detects in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a principle explanatory view of light quantity correction performed in the light quantity correction circuit 93 in the image display device LSD according to one embodiment of the present invention. It is the 1st explanatory view about light quantity amendment circuit 93 in image display device LSD concerning one embodiment of the present invention. It is a 2nd explanatory drawing regarding the light quantity correction circuit 93 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a 3rd explanatory drawing regarding the light quantity correction circuit 93 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a detailed block diagram of the light quantity correction circuit 93 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is explanatory drawing regarding the initial setting operation | movement performed in the light quantity correction circuit 93 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a flowchart which shows the initial setting operation | movement performed in the light quantity correction circuit 93 in the image display apparatus LSD which concerns on one Embodiment of this invention. It is a timing chart which shows steady operation of image display device LSD concerning one embodiment of the present invention. It is the 1st explanatory view about the modification of image display device LSD concerning one embodiment of the present invention. It is the 2nd explanatory view about the modification of image display device LSD concerning one embodiment of the present invention. It is the 3rd explanatory view about the modification of image display device LSD concerning one embodiment of the present invention.

Explanation of symbols

  LSD ... Image display device, 10 ... Video signal processing circuit, 20R ... Red laser driver, 20G ... Green laser driver, 20B ... Blue laser driver, 30R ... Red laser diode, 30G ... Green laser diode, 30B ... Blue laser diode, 40 DESCRIPTION OF SYMBOLS ... Optical system for optical axis alignment, 50 ... Laser scanning part, 60 ... Scanning drive part, 70 ... Irradiation position detection part, 80 ... Pixel synchronous clock generation circuit, 90 ... Photoelectric conversion element, 91 ... I / V converter, 92 ... A / D converter, 93 ... Light quantity correction circuit, 94, 95 ... D / A converter, 100 ... Screen

Claims (9)

A light source device comprising a light source and drive signal generation means for supplying a drive signal to the light source,
A light amount measuring means for measuring the light amount of the light source;
The difference between the target light amount according to the gradation value indicated by the gradation data input from the outside and the light amount measured by the light amount measuring means is calculated as a light amount error, and the amount of light with respect to the change amount of the drive signal of the light source is calculated. The differential efficiency defined by the amount of change is corrected by an integrated value of the product of the light amount error and the gradation value, and the threshold value of the drive signal necessary for causing the light source to emit light is set to the light amount error. A light amount correction unit that outputs a command signal to the drive signal generation unit so as to generate a drive signal having a corrected differential efficiency and a threshold value after correction.
A light source device comprising: The drive signal generation means includes
Gradation current generation means for generating gradation current according to the gradation value based on the gradation value indicated by gradation data input from the outside and the gradation current command signal input from the light amount correction means When,
Threshold current generation means for generating a threshold current according to a threshold current command signal input from the light amount correction means;
Current adding means for supplying an addition current of the gradation current and the threshold current to the light source as the drive signal;
The light amount correction means includes
The current value of the first variable corresponding to the differential efficiency as the differential efficiency after correction is a numerical value proportional to the integrated value of the product of the light amount error and the gradation value from the previous value of the first variable. The gradation current command signal corresponding to the current value of the first variable is output to the gradation current generation means, and the second variable corresponding to the threshold is used as the corrected threshold. Is obtained by subtracting a numerical value proportional to the integrated value of the light amount error from the previous value of the second variable, and the threshold current command signal corresponding to the current value of the second variable is determined as the threshold value. Output to the current generation means,
The light source device according to claim 1. The light amount correction means includes
As a gradation value used when calculating the product of the light amount error and the gradation value, an average value of the gradation values, a preset gradation value, or a minimum gradation value to a maximum gradation value The light source device according to claim 1, wherein a difference between the intermediate value and the gradation value is used. The light amount correction means includes
When calculating an integrated value of the product of the light amount error and the gradation value, the weighting constant is sequentially multiplied from the product value of the past light amount error and the gradation value, and the light amount error is calculated. 4. The light source device according to claim 1, wherein when the integrated value is obtained, a weighting constant that is sequentially forgotten from a past light amount error value is multiplied. The light amount correction means includes
At the time of turning on the power, as an initial setting operation for correcting the offset of the measurement light quantity that the light quantity measurement means has,
After obtaining the measured light amount as a black level light amount when the gradation current command signal, the threshold current command signal and the gradation data for outputting the light source completely to the drive signal generating means are obtained, When a value obtained by increasing the threshold current command signal and subtracting the black level light amount from the measured light amount reaches a first set light amount that defines a predetermined brightness, the threshold current command signal is decreased and the measured light amount The threshold current command signal when the value obtained by subtracting the black level light amount from the second set light amount regarded as the black level is set as the initial value of the threshold current command signal, while the maximum gradation value Is output to the drive signal generating means, the gradation current command signal is increased, and a value obtained by subtracting the black level light amount from the measured light amount defines a third set light that defines the maximum target light emission amount. The light source device according to any one of claims 2 to 4 of the gradation current command signal and sets the initial value of the gradation current command signal when reached. The light amount correction means includes
The initial value of the threshold current command signal obtained by the initial setting operation is used as the previous value of the second variable when obtaining the current value of the second variable for the first time, and the gradation current command signal 6. The light source device according to claim 5, wherein the initial value is used as the previous value of the first variable when the current value of the first variable is calculated for the first time. An image display device that displays light by scanning light on a projection surface,
The light source device according to any one of claims 1 to 6,
Scanning means for scanning the projection surface with light generated from a light source in the light source device;
Based on a video signal supplied from the outside, the gradation data representing an image to be displayed is generated, and gradation data corresponding to the irradiation position of the light on the projection surface is generated as a drive signal in the light source device. Video signal processing means for outputting to the generating means and the light amount correcting means;
An image display device comprising: In a period of not scanning light on the projection surface,
The video signal processing means outputs predetermined gradation data to a drive signal generation means and a light amount correction means in the light source device,
The light amount correction unit performs the correction based on the light amount of the light source corresponding to the predetermined gradation data measured by the light amount measurement unit and the gradation value indicated by the predetermined gradation data. 8. The image display apparatus according to claim 7, wherein A light amount correction method used in a light source device including a light source and a drive signal generation unit that supplies a drive signal to the light source,
A first step of measuring the light quantity of the light source;
A second step of calculating, as a light amount error, a difference between a target light amount corresponding to a gradation value indicated by gradation data input from the outside and a light amount measured in the first step;
A third step of obtaining an integrated value of a product of the light amount error and the gradation value;
A fourth step of correcting the differential efficiency defined by the amount of change in the amount of light with respect to the amount of change in the drive signal of the light source by an integrated value of the product of the light amount error and the gradation value;
A fifth step of obtaining an integrated value of the light amount error;
A sixth step of correcting a threshold value of the drive signal, which is the minimum necessary for causing the light source to emit light, by an integrated value of the light amount error;
A seventh step of outputting, to the drive signal generation means, a command signal that generates a drive signal having the corrected differential efficiency and threshold value;
A light amount correction method characterized by comprising:

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